2015-04-24 08:33:23 +02:00
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/*-------------------------------------------------------------------------
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*
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* execIndexing.c
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2015-04-24 20:12:32 +02:00
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* routines for inserting index tuples and enforcing unique and
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* exclusive constraints.
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*
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* ExecInsertIndexTuples() is the main entry point. It's called after
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* inserting a tuple to the heap, and it inserts corresponding index tuples
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* into all indexes. At the same time, it enforces any unique and
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* exclusion constraints:
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*
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* Unique Indexes
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* --------------
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*
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* Enforcing a unique constraint is straightforward. When the index AM
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* inserts the tuple to the index, it also checks that there are no
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* conflicting tuples in the index already. It does so atomically, so that
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* even if two backends try to insert the same key concurrently, only one
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* of them will succeed. All the logic to ensure atomicity, and to wait
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* for in-progress transactions to finish, is handled by the index AM.
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*
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* If a unique constraint is deferred, we request the index AM to not
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* throw an error if a conflict is found. Instead, we make note that there
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* was a conflict and return the list of indexes with conflicts to the
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* caller. The caller must re-check them later, by calling index_insert()
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* with the UNIQUE_CHECK_EXISTING option.
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*
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* Exclusion Constraints
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* ---------------------
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*
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* Exclusion constraints are different from unique indexes in that when the
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* tuple is inserted to the index, the index AM does not check for
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* duplicate keys at the same time. After the insertion, we perform a
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* separate scan on the index to check for conflicting tuples, and if one
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* is found, we throw an error and the transaction is aborted. If the
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* conflicting tuple's inserter or deleter is in-progress, we wait for it
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* to finish first.
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*
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* There is a chance of deadlock, if two backends insert a tuple at the
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* same time, and then perform the scan to check for conflicts. They will
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* find each other's tuple, and both try to wait for each other. The
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* deadlock detector will detect that, and abort one of the transactions.
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* That's fairly harmless, as one of them was bound to abort with a
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* "duplicate key error" anyway, although you get a different error
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* message.
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*
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* If an exclusion constraint is deferred, we still perform the conflict
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* checking scan immediately after inserting the index tuple. But instead
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* of throwing an error if a conflict is found, we return that information
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* to the caller. The caller must re-check them later by calling
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* check_exclusion_constraint().
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*
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2015-04-24 08:33:23 +02:00
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*
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* Portions Copyright (c) 1996-2015, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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*
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* IDENTIFICATION
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* src/backend/executor/execIndexing.c
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*
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*-------------------------------------------------------------------------
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*/
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#include "postgres.h"
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#include "access/relscan.h"
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#include "catalog/index.h"
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#include "executor/executor.h"
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#include "nodes/nodeFuncs.h"
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#include "storage/lmgr.h"
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#include "utils/tqual.h"
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static bool index_recheck_constraint(Relation index, Oid *constr_procs,
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Datum *existing_values, bool *existing_isnull,
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Datum *new_values);
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/* ----------------------------------------------------------------
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* ExecOpenIndices
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*
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* Find the indices associated with a result relation, open them,
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* and save information about them in the result ResultRelInfo.
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*
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* At entry, caller has already opened and locked
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* resultRelInfo->ri_RelationDesc.
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* ----------------------------------------------------------------
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*/
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void
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ExecOpenIndices(ResultRelInfo *resultRelInfo)
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{
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Relation resultRelation = resultRelInfo->ri_RelationDesc;
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List *indexoidlist;
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ListCell *l;
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int len,
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i;
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RelationPtr relationDescs;
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IndexInfo **indexInfoArray;
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resultRelInfo->ri_NumIndices = 0;
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/* fast path if no indexes */
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if (!RelationGetForm(resultRelation)->relhasindex)
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return;
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/*
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* Get cached list of index OIDs
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*/
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indexoidlist = RelationGetIndexList(resultRelation);
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len = list_length(indexoidlist);
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if (len == 0)
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return;
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/*
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* allocate space for result arrays
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*/
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relationDescs = (RelationPtr) palloc(len * sizeof(Relation));
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indexInfoArray = (IndexInfo **) palloc(len * sizeof(IndexInfo *));
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resultRelInfo->ri_NumIndices = len;
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resultRelInfo->ri_IndexRelationDescs = relationDescs;
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resultRelInfo->ri_IndexRelationInfo = indexInfoArray;
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/*
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* For each index, open the index relation and save pg_index info. We
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* acquire RowExclusiveLock, signifying we will update the index.
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*
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* Note: we do this even if the index is not IndexIsReady; it's not worth
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* the trouble to optimize for the case where it isn't.
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*/
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i = 0;
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foreach(l, indexoidlist)
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{
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Oid indexOid = lfirst_oid(l);
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Relation indexDesc;
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IndexInfo *ii;
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indexDesc = index_open(indexOid, RowExclusiveLock);
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/* extract index key information from the index's pg_index info */
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ii = BuildIndexInfo(indexDesc);
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relationDescs[i] = indexDesc;
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indexInfoArray[i] = ii;
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i++;
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}
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list_free(indexoidlist);
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}
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/* ----------------------------------------------------------------
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* ExecCloseIndices
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*
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* Close the index relations stored in resultRelInfo
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* ----------------------------------------------------------------
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*/
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void
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ExecCloseIndices(ResultRelInfo *resultRelInfo)
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{
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int i;
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int numIndices;
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RelationPtr indexDescs;
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numIndices = resultRelInfo->ri_NumIndices;
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indexDescs = resultRelInfo->ri_IndexRelationDescs;
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for (i = 0; i < numIndices; i++)
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{
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if (indexDescs[i] == NULL)
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continue; /* shouldn't happen? */
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/* Drop lock acquired by ExecOpenIndices */
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index_close(indexDescs[i], RowExclusiveLock);
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}
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/*
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* XXX should free indexInfo array here too? Currently we assume that
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* such stuff will be cleaned up automatically in FreeExecutorState.
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*/
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}
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/* ----------------------------------------------------------------
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* ExecInsertIndexTuples
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*
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* This routine takes care of inserting index tuples
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* into all the relations indexing the result relation
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* when a heap tuple is inserted into the result relation.
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*
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2015-04-24 20:12:32 +02:00
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* Unique and exclusion constraints are enforced at the same
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* time. This returns a list of index OIDs for any unique or
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* exclusion constraints that are deferred and that had
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2015-04-24 08:33:23 +02:00
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* potential (unconfirmed) conflicts.
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*
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* CAUTION: this must not be called for a HOT update.
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* We can't defend against that here for lack of info.
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* Should we change the API to make it safer?
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* ----------------------------------------------------------------
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*/
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List *
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ExecInsertIndexTuples(TupleTableSlot *slot,
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ItemPointer tupleid,
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EState *estate)
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{
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List *result = NIL;
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ResultRelInfo *resultRelInfo;
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int i;
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int numIndices;
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RelationPtr relationDescs;
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Relation heapRelation;
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IndexInfo **indexInfoArray;
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ExprContext *econtext;
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Datum values[INDEX_MAX_KEYS];
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bool isnull[INDEX_MAX_KEYS];
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/*
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* Get information from the result relation info structure.
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*/
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resultRelInfo = estate->es_result_relation_info;
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numIndices = resultRelInfo->ri_NumIndices;
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relationDescs = resultRelInfo->ri_IndexRelationDescs;
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indexInfoArray = resultRelInfo->ri_IndexRelationInfo;
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heapRelation = resultRelInfo->ri_RelationDesc;
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/*
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* We will use the EState's per-tuple context for evaluating predicates
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* and index expressions (creating it if it's not already there).
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*/
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econtext = GetPerTupleExprContext(estate);
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/* Arrange for econtext's scan tuple to be the tuple under test */
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econtext->ecxt_scantuple = slot;
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/*
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* for each index, form and insert the index tuple
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*/
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for (i = 0; i < numIndices; i++)
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{
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Relation indexRelation = relationDescs[i];
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IndexInfo *indexInfo;
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IndexUniqueCheck checkUnique;
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bool satisfiesConstraint;
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if (indexRelation == NULL)
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continue;
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indexInfo = indexInfoArray[i];
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/* If the index is marked as read-only, ignore it */
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if (!indexInfo->ii_ReadyForInserts)
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continue;
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/* Check for partial index */
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if (indexInfo->ii_Predicate != NIL)
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{
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List *predicate;
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/*
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* If predicate state not set up yet, create it (in the estate's
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* per-query context)
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*/
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predicate = indexInfo->ii_PredicateState;
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if (predicate == NIL)
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{
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predicate = (List *)
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ExecPrepareExpr((Expr *) indexInfo->ii_Predicate,
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estate);
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indexInfo->ii_PredicateState = predicate;
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}
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/* Skip this index-update if the predicate isn't satisfied */
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if (!ExecQual(predicate, econtext, false))
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continue;
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}
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/*
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* FormIndexDatum fills in its values and isnull parameters with the
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* appropriate values for the column(s) of the index.
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*/
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FormIndexDatum(indexInfo,
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slot,
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estate,
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values,
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isnull);
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/*
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* The index AM does the actual insertion, plus uniqueness checking.
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*
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* For an immediate-mode unique index, we just tell the index AM to
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* throw error if not unique.
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*
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* For a deferrable unique index, we tell the index AM to just detect
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* possible non-uniqueness, and we add the index OID to the result
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* list if further checking is needed.
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*/
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if (!indexRelation->rd_index->indisunique)
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checkUnique = UNIQUE_CHECK_NO;
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else if (indexRelation->rd_index->indimmediate)
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checkUnique = UNIQUE_CHECK_YES;
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else
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checkUnique = UNIQUE_CHECK_PARTIAL;
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satisfiesConstraint =
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index_insert(indexRelation, /* index relation */
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values, /* array of index Datums */
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isnull, /* null flags */
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tupleid, /* tid of heap tuple */
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heapRelation, /* heap relation */
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checkUnique); /* type of uniqueness check to do */
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/*
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* If the index has an associated exclusion constraint, check that.
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* This is simpler than the process for uniqueness checks since we
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* always insert first and then check. If the constraint is deferred,
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* we check now anyway, but don't throw error on violation; instead
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* we'll queue a recheck event.
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*
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* An index for an exclusion constraint can't also be UNIQUE (not an
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* essential property, we just don't allow it in the grammar), so no
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* need to preserve the prior state of satisfiesConstraint.
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*/
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if (indexInfo->ii_ExclusionOps != NULL)
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{
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bool errorOK = !indexRelation->rd_index->indimmediate;
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satisfiesConstraint =
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check_exclusion_constraint(heapRelation,
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indexRelation, indexInfo,
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tupleid, values, isnull,
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estate, false, errorOK);
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}
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if ((checkUnique == UNIQUE_CHECK_PARTIAL ||
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indexInfo->ii_ExclusionOps != NULL) &&
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!satisfiesConstraint)
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{
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/*
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* The tuple potentially violates the uniqueness or exclusion
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* constraint, so make a note of the index so that we can re-check
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* it later.
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*/
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result = lappend_oid(result, RelationGetRelid(indexRelation));
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}
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}
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return result;
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}
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/*
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* Check for violation of an exclusion constraint
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*
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* heap: the table containing the new tuple
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* index: the index supporting the exclusion constraint
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* indexInfo: info about the index, including the exclusion properties
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* tupleid: heap TID of the new tuple we have just inserted
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* values, isnull: the *index* column values computed for the new tuple
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* estate: an EState we can do evaluation in
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* newIndex: if true, we are trying to build a new index (this affects
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* only the wording of error messages)
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* errorOK: if true, don't throw error for violation
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*
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* Returns true if OK, false if actual or potential violation
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*
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* When errorOK is true, we report violation without waiting to see if any
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* concurrent transaction has committed or not; so the violation is only
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* potential, and the caller must recheck sometime later. This behavior
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* is convenient for deferred exclusion checks; we need not bother queuing
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* a deferred event if there is definitely no conflict at insertion time.
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*
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* When errorOK is false, we'll throw error on violation, so a false result
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* is impossible.
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*/
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bool
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check_exclusion_constraint(Relation heap, Relation index, IndexInfo *indexInfo,
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ItemPointer tupleid, Datum *values, bool *isnull,
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EState *estate, bool newIndex, bool errorOK)
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{
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Oid *constr_procs = indexInfo->ii_ExclusionProcs;
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uint16 *constr_strats = indexInfo->ii_ExclusionStrats;
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Oid *index_collations = index->rd_indcollation;
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int index_natts = index->rd_index->indnatts;
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IndexScanDesc index_scan;
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HeapTuple tup;
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|
ScanKeyData scankeys[INDEX_MAX_KEYS];
|
|
|
|
SnapshotData DirtySnapshot;
|
|
|
|
int i;
|
|
|
|
bool conflict;
|
|
|
|
bool found_self;
|
|
|
|
ExprContext *econtext;
|
|
|
|
TupleTableSlot *existing_slot;
|
|
|
|
TupleTableSlot *save_scantuple;
|
|
|
|
|
|
|
|
/*
|
|
|
|
* If any of the input values are NULL, the constraint check is assumed to
|
|
|
|
* pass (i.e., we assume the operators are strict).
|
|
|
|
*/
|
|
|
|
for (i = 0; i < index_natts; i++)
|
|
|
|
{
|
|
|
|
if (isnull[i])
|
|
|
|
return true;
|
|
|
|
}
|
|
|
|
|
|
|
|
/*
|
|
|
|
* Search the tuples that are in the index for any violations, including
|
|
|
|
* tuples that aren't visible yet.
|
|
|
|
*/
|
|
|
|
InitDirtySnapshot(DirtySnapshot);
|
|
|
|
|
|
|
|
for (i = 0; i < index_natts; i++)
|
|
|
|
{
|
|
|
|
ScanKeyEntryInitialize(&scankeys[i],
|
|
|
|
0,
|
|
|
|
i + 1,
|
|
|
|
constr_strats[i],
|
|
|
|
InvalidOid,
|
|
|
|
index_collations[i],
|
|
|
|
constr_procs[i],
|
|
|
|
values[i]);
|
|
|
|
}
|
|
|
|
|
|
|
|
/*
|
|
|
|
* Need a TupleTableSlot to put existing tuples in.
|
|
|
|
*
|
|
|
|
* To use FormIndexDatum, we have to make the econtext's scantuple point
|
|
|
|
* to this slot. Be sure to save and restore caller's value for
|
|
|
|
* scantuple.
|
|
|
|
*/
|
|
|
|
existing_slot = MakeSingleTupleTableSlot(RelationGetDescr(heap));
|
|
|
|
|
|
|
|
econtext = GetPerTupleExprContext(estate);
|
|
|
|
save_scantuple = econtext->ecxt_scantuple;
|
|
|
|
econtext->ecxt_scantuple = existing_slot;
|
|
|
|
|
|
|
|
/*
|
|
|
|
* May have to restart scan from this point if a potential conflict is
|
|
|
|
* found.
|
|
|
|
*/
|
|
|
|
retry:
|
|
|
|
conflict = false;
|
|
|
|
found_self = false;
|
|
|
|
index_scan = index_beginscan(heap, index, &DirtySnapshot, index_natts, 0);
|
|
|
|
index_rescan(index_scan, scankeys, index_natts, NULL, 0);
|
|
|
|
|
|
|
|
while ((tup = index_getnext(index_scan,
|
|
|
|
ForwardScanDirection)) != NULL)
|
|
|
|
{
|
|
|
|
TransactionId xwait;
|
|
|
|
ItemPointerData ctid_wait;
|
|
|
|
Datum existing_values[INDEX_MAX_KEYS];
|
|
|
|
bool existing_isnull[INDEX_MAX_KEYS];
|
|
|
|
char *error_new;
|
|
|
|
char *error_existing;
|
|
|
|
|
|
|
|
/*
|
|
|
|
* Ignore the entry for the tuple we're trying to check.
|
|
|
|
*/
|
|
|
|
if (ItemPointerEquals(tupleid, &tup->t_self))
|
|
|
|
{
|
|
|
|
if (found_self) /* should not happen */
|
|
|
|
elog(ERROR, "found self tuple multiple times in index \"%s\"",
|
|
|
|
RelationGetRelationName(index));
|
|
|
|
found_self = true;
|
|
|
|
continue;
|
|
|
|
}
|
|
|
|
|
|
|
|
/*
|
|
|
|
* Extract the index column values and isnull flags from the existing
|
|
|
|
* tuple.
|
|
|
|
*/
|
|
|
|
ExecStoreTuple(tup, existing_slot, InvalidBuffer, false);
|
|
|
|
FormIndexDatum(indexInfo, existing_slot, estate,
|
|
|
|
existing_values, existing_isnull);
|
|
|
|
|
|
|
|
/* If lossy indexscan, must recheck the condition */
|
|
|
|
if (index_scan->xs_recheck)
|
|
|
|
{
|
|
|
|
if (!index_recheck_constraint(index,
|
|
|
|
constr_procs,
|
|
|
|
existing_values,
|
|
|
|
existing_isnull,
|
|
|
|
values))
|
|
|
|
continue; /* tuple doesn't actually match, so no
|
|
|
|
* conflict */
|
|
|
|
}
|
|
|
|
|
|
|
|
/*
|
|
|
|
* At this point we have either a conflict or a potential conflict. If
|
|
|
|
* we're not supposed to raise error, just return the fact of the
|
|
|
|
* potential conflict without waiting to see if it's real.
|
|
|
|
*/
|
|
|
|
if (errorOK)
|
|
|
|
{
|
|
|
|
conflict = true;
|
|
|
|
break;
|
|
|
|
}
|
|
|
|
|
|
|
|
/*
|
|
|
|
* If an in-progress transaction is affecting the visibility of this
|
|
|
|
* tuple, we need to wait for it to complete and then recheck. For
|
|
|
|
* simplicity we do rechecking by just restarting the whole scan ---
|
|
|
|
* this case probably doesn't happen often enough to be worth trying
|
|
|
|
* harder, and anyway we don't want to hold any index internal locks
|
|
|
|
* while waiting.
|
|
|
|
*/
|
|
|
|
xwait = TransactionIdIsValid(DirtySnapshot.xmin) ?
|
|
|
|
DirtySnapshot.xmin : DirtySnapshot.xmax;
|
|
|
|
|
|
|
|
if (TransactionIdIsValid(xwait))
|
|
|
|
{
|
|
|
|
ctid_wait = tup->t_data->t_ctid;
|
|
|
|
index_endscan(index_scan);
|
|
|
|
XactLockTableWait(xwait, heap, &ctid_wait,
|
|
|
|
XLTW_RecheckExclusionConstr);
|
|
|
|
goto retry;
|
|
|
|
}
|
|
|
|
|
|
|
|
/*
|
|
|
|
* We have a definite conflict. Report it.
|
|
|
|
*/
|
|
|
|
error_new = BuildIndexValueDescription(index, values, isnull);
|
|
|
|
error_existing = BuildIndexValueDescription(index, existing_values,
|
|
|
|
existing_isnull);
|
|
|
|
if (newIndex)
|
|
|
|
ereport(ERROR,
|
|
|
|
(errcode(ERRCODE_EXCLUSION_VIOLATION),
|
|
|
|
errmsg("could not create exclusion constraint \"%s\"",
|
|
|
|
RelationGetRelationName(index)),
|
|
|
|
error_new && error_existing ?
|
|
|
|
errdetail("Key %s conflicts with key %s.",
|
|
|
|
error_new, error_existing) :
|
|
|
|
errdetail("Key conflicts exist."),
|
|
|
|
errtableconstraint(heap,
|
|
|
|
RelationGetRelationName(index))));
|
|
|
|
else
|
|
|
|
ereport(ERROR,
|
|
|
|
(errcode(ERRCODE_EXCLUSION_VIOLATION),
|
|
|
|
errmsg("conflicting key value violates exclusion constraint \"%s\"",
|
|
|
|
RelationGetRelationName(index)),
|
|
|
|
error_new && error_existing ?
|
|
|
|
errdetail("Key %s conflicts with existing key %s.",
|
|
|
|
error_new, error_existing) :
|
|
|
|
errdetail("Key conflicts with existing key."),
|
|
|
|
errtableconstraint(heap,
|
|
|
|
RelationGetRelationName(index))));
|
|
|
|
}
|
|
|
|
|
|
|
|
index_endscan(index_scan);
|
|
|
|
|
|
|
|
/*
|
|
|
|
* Ordinarily, at this point the search should have found the originally
|
|
|
|
* inserted tuple, unless we exited the loop early because of conflict.
|
|
|
|
* However, it is possible to define exclusion constraints for which that
|
|
|
|
* wouldn't be true --- for instance, if the operator is <>. So we no
|
|
|
|
* longer complain if found_self is still false.
|
|
|
|
*/
|
|
|
|
|
|
|
|
econtext->ecxt_scantuple = save_scantuple;
|
|
|
|
|
|
|
|
ExecDropSingleTupleTableSlot(existing_slot);
|
|
|
|
|
|
|
|
return !conflict;
|
|
|
|
}
|
|
|
|
|
|
|
|
/*
|
|
|
|
* Check existing tuple's index values to see if it really matches the
|
|
|
|
* exclusion condition against the new_values. Returns true if conflict.
|
|
|
|
*/
|
|
|
|
static bool
|
|
|
|
index_recheck_constraint(Relation index, Oid *constr_procs,
|
|
|
|
Datum *existing_values, bool *existing_isnull,
|
|
|
|
Datum *new_values)
|
|
|
|
{
|
|
|
|
int index_natts = index->rd_index->indnatts;
|
|
|
|
int i;
|
|
|
|
|
|
|
|
for (i = 0; i < index_natts; i++)
|
|
|
|
{
|
|
|
|
/* Assume the exclusion operators are strict */
|
|
|
|
if (existing_isnull[i])
|
|
|
|
return false;
|
|
|
|
|
|
|
|
if (!DatumGetBool(OidFunctionCall2Coll(constr_procs[i],
|
|
|
|
index->rd_indcollation[i],
|
|
|
|
existing_values[i],
|
|
|
|
new_values[i])))
|
|
|
|
return false;
|
|
|
|
}
|
|
|
|
|
|
|
|
return true;
|
|
|
|
}
|